This invention relates generally to methods of back flushing filters and more particularly to an improved back flushing filter construction which finds particular utility when used in the meat treating industry to filter liquid formulas that are injected into poultry, beef or pork by an injection machine by means of a pump that pumps the formulas into the meat through needles with small inlet and outlets.
The prior art is exemplified by prior issued patents such as U.S. Pat. No. 2,918,172 issued Dec.22, 1959, U.S. Pat. No. 3,074,560 issued Jan. 22, 1963 and U.S. Pat. No. 3,635,348 issued Jan. 18, 1972. With the constructions disclosed and claimed in those prior art patents, filter baskets capable of either continuous or intermittent rotation are cleaned with a doctor blade and may be additionally cleaned by a back-flushing shoe disposed inside of the basket and arranged to eject a narrow jet of liquid through a localized section of the filter basket to back-flush the filter openings as they move by the shoe.
Other prior art in the filtering art of conceivable interest includes such patents as U.S. Pat. No. 4,631,126; 4,762,615; 4,818,402; 4,931,180; 5,128,029; and 5,171,433. For example, a cleaning nozzle may be used to apply flushing liquid to a stack of discs that loosen when rotated in an opposite direction. Other forms of back wash arms are also disclosed.
The present invention contemplates the utilization of a large stainless steel cylindrical filter basket, or cylinder, which can be disposed in the tub or tank of a liquid stream system having a plurality of filtering stages. The cylinder walls are perforated to form an array of filter openings, which may be so small that they get stopped up with tiny pieces of meat and ingredients in the liquid formulas flowing in the liquid stream.
Within the cylinder a disc plunger, or piston, is moved in a cylinder/piston relationship to compress and move effluent collected in the cylinder to back-flush the filter openings and creating a rolling action of the liquid all around the filter basket.
The operation of the filter and its back-flushing feature is automated by placing the disk plunger or piston under the control of a motor means controlled by an automatic cycling machine, thereby to cycle the disk plunger or piston through a series of reciprocations within the cylinder alternated with a period of rest. The result is a greatly enhanced and lengthened effective life cycle for the filtering system before shut-down and clean up is necessary.